nyoj 5 Binary String Matching(kmp)

Binary String Matching

 

 

描述

Given two strings A and B, whose alphabet consist only ‘0’ and ‘1’. Your task is only to tell how many times does A appear as a substring of B? For example, the text string B is ‘1001110110’ while the pattern string A is ‘11’, you should output 3, because the pattern A appeared at the posit

 

输入

The first line consist only one integer N, indicates N cases follows. In each case, there are two lines, the first line gives the string A, length (A) <= 10, and the second line gives the string B, length (B) <= 1000. And it is guaranteed that B is always longer than A.

输出

For each case, output a single line consist a single integer, tells how many times do B appears as a substring of A.

样例输入

3
11
1001110110
101
110010010010001
1010
110100010101011 

样例输出

3
0
3 

#include<cstdio>
#include<cstring>
using namespace std;

int next[105];

void getnext(char *s)
{
    int len=strlen(s);
    int i=0,j=-1;
    next[i]=j;
    while(i<len)
    {
        if(j==-1||s[i]==s[j])
        {
            i++;
            j++;
            next[i]=j;
        }
        else
            j=next[j];
    }
}

int kmp(char *s1,char *s2)
{
    int res=0;
    int len1=strlen(s1);
    int len2=strlen(s2);
    getnext(s2);
    int i=0,j=0;
    while(i<len1)
    {
        if(j==-1||s1[i]==s2[j])
        {
            i++;
            j++;
            if(j==len2)
                res++;
        }
        else
            j=next[j];
    }
    return res;
}

int main()
{
    int T;
    char sub[15],s[1005];
    scanf("%d",&T);
    while(T--)
    {
        scanf("%s",sub);
        scanf("%s",s);
        getnext(sub);
        int ans=kmp(s,sub);
        printf("%d\n",ans);
    }
    return 0;
}